High-grade serous ovarian carcinoma (HGSOC) is an aggressive and deadly form of ovarian cancer, yet its pathogenesis is poorly understood. BRCA1 and BRCA2 mutations (identified in 10-40% of patients) are important risk factor for HGSOC. If inactivation of BRCA1/2 is critical in the early transformation of fallopian tube secretory epithelial (FTSE) cells, then other regulatory mechanisms must block BRCA1/2 in the remaining 60% of HGSOC cases. Recent identification of miR-182 repression of BRCA1 expression suggested a role for microRNA in the regulation of BRCA1 expression. MiR-182 is one of a few microRNAs overexpressed in cells with DNA damage and abnormal overexpression early and later stages of PSC. We hypothesize that miR-182 overexpression is an early genetic event and an important trigger of tumorigenesis in HGSOC through dysregulation of HGSOC associated genes. To test our hypothesis, we propose the following specific aims: AIM 1: Investigate the cellular and molecular mechanisms of miR-182-mediated tumorigenesis in FTSE cells in vitro. We propose that impaired DNA damage repair mechanisms and early tumorigenesis in FTSE cells is due to a dysregulation of miR-182 and its target genes. To test our hypothesis, we will examine 1) how miR-182 responds to DNA damage in FTSE cells and whether IR-induced miR-182 overexpression requires mutant P53; and 2) the kinetics of DNA damage repair in FTSE cells in the presence and absence of miR-182. We will also investigate whether miR-182- mediated tumorigenesis can be enhanced by negative regulation of its predicted target genes BNC2 and MTSS1. AIM 2: Test if miR-182 overexpression in FTSE results in tumor formation in xenografts and examine if knockdown of miR-182 expression reduce tumor burden and metastasis in ovarian cancer in vivo. Introducing miR-182 overexpression can result in tumor transformation and enhance invasion and metastasis. We observed that silencing of miR-182 expression in vitro significantly reduced aggressive cell behavior in normal FTSE and ovarian cancer cells. In this study, we will examine ovarian tumor cell growth, invasion, and metastasis in xenografts of nude mice by controlling miR-182 expression. The effectiveness of anti-miR-182 in treated tumors will be evaluated by examination of miR-182 and its target gene expression. If the proposed aims are achieved, we will design experiments for testing the therapeutic effects of conditional activation of miR-182 overexpression in mice, which mimics to early molecular changes in human HGSOC. The ultimate goals are to develop clinical trials in early prevention and a sensitive diagnostic test i detecting early STIC.